If you want to respond to someone that made a comment on your wall just click on that persons picture and it will take you to their page scroll down to their wall write something nd then click submit and you are done.There is a lot of information and things to do here, like joining groups, discussion groups, making friends etc, there is a lot to do here.If you have any questions just leave a message on the page where you retrieve your messages from or their comment wall and we will help you